Moving onto High Steps for a Four-limbed Robot with Torso Contact*

In this paper, we describe approaches to enable a four-limbed robot to get over a step higher than its leg with torso contact. The higher the step becomes, the more difficult it is for legged robots to get over from the viewpoint of stability and kinematic reachability. Torso landing contributes to improving stability and robustness of motion for moving onto high step because of lower center of mass (CoM) and larger support polygon, which is seldomly utilized by previous human-sized legged robots. The approaches in this paper consist of the following two components. As for hardware, spikes are arranged on the bottom of robot’ s body for stable torso landing on a high step. As for motion generation, Sequential Quadratic Programming (SQP) is utilized to generate motion with torso landing to guarantee stability of robots during getting over the high step. From experiments, it is confirmed that the fourlimbed robot WAREC-I succeeded in moving onto a step with the height of 865mm.